There's a thread on how to do this with the Mogul
here.
I briefly looked at this option before because I was interested in flashing a different phone from sprint to MetroPCS. I think the answer is, yes it can be done, but not easily.
I think to get data and mms working takes a lot of effort, and I'm not 100% sure it can even be done at all.
I know MetroPCS can flash a lot of different phones for you right in the stores, but I also know that they don't like to do it. You may want to check that option first. If they don't want to do it, insist you understand the consequences and ask them again. If not, you can try looking at the other thread and see how viable it is for you to complete the steps outlined there.
Good luck.
There is another forum I found that talks about how to flash your specific phone. I suggest you check it out
here.
ESN cloning is something that is illegal, so therefore it does not explicitly describe any method to do it.
PM the guy who started that thread over there and you might have your answer.